The Islamic State swept into Mosul in June 2014, seizing Iraq's second city from the government's weakened forces in a stunning victory for the extremist group, allowing it to capture vast amounts of heavy weapons and equipment.
By the end of the month, the group claimed it had formed a caliphate, or Islamic state, and demanded allegiance from all Muslims. In July, the militia's leader, Abu Bakr al-Baghdadi appeared in a mosque in Mosul to deliver a sermon, his first major public appearance.
Now Mosul - which prior to the takeover had more than 2 million residents - is facing a joint attack by the United States-led coalition in the air and Iraqi troops on the ground.
Before the 2003 US-led invasion of Iraq, the subsequent civil war and the Islamic State capture of the city, Mosul was extremely diverse. It was home to ancient religions and Christian sects dating back nearly 2,000 years.
Taking the city back from Islamic State would be a victory for the fragile Iraqi state, and a major blow to the radical Sunni group which would cede its most important city and face a reversal of its efforts to homogenize areas under its control, efforts that included crushing everyone who is not a Sunni Muslim.
But the group is deeply entrenched in civilian areas in Iraq and for disenfranchised Sunni Arabs, remains a pillar of stability in a chaotic region, offering governing structures amid anarchy.
In Syria, the government's ground troops and Russian airstrikes are attacking Islamic State in the ancient city of Palmyra. If successful, this push would deprive Islamic State of its only major city in central Syria.
In eastern Syria, fighters from the Kurds' so-called People's Protection Units allied with some Arab troops in the wider Syrian Democratic Forces are - village by village - depriving Islamic State of key stretches of territory along the Khabur River.
The offensive could help cut off the Islamic State in Syria from the main border crossing to Iraq, where the group still controls areas in the west of the country, in addition to its northern territories.
The Syrian government is also pushing against Islamic State east of Aleppo in the country's north.
However, the so-called Manbij pocket between Aleppo and the Euphrates River, including the last stretch of land held by the extremists along the Turkish border, still remains under full Islamic State control.
A joint Turkish-Kurdish would be advantageous against the extremists but for a number of reasons - including the long-standing conflict between Turkey and its Kurdish minority - Ankara is unwilling to cooperate with the Kurdish forces in Syria, despite US efforts to change this.
In 2014 the Islamic State's advance seemed unstoppable. It is now slowly being pushed back but far from defeated.